This application relates to an improved architecture for a high performance microprocessor integrated circuit. More particularly, it relates to such a microprocessor system architecture which allows computed results to be fed back in real time to other parts of embedded computer systems. Most especially, this invention relates to such a microprocessor system architecture which allows the provision of a single chip very large scale integration (VLSI) 16-bit bipolar microprocessor with floating point as well as fixed point arithmetic and extensive real time processing capabilities.
Commercially available microprocessor integrated circuits, such as an F9445 microprocessor integrated circuit, obtainable from Fairchild Camera & Instrument Corporation, Mountain View, Calif.; an Intel 8080, 8088, or 8087, obtainable from Intel Corporation, Santa Clara, Calif.; a Motorola 6800 or 68000, obtainable from Motorola, Inc., Phoenix, Ariz.; or a National Semiconductor 16000, obtainable from National Semiconductor Corporation, Santa Clara, Calif., all employ a series of elemental instructions called microcode for causing the microprocessors to carry out operations on data supplied to them. The microcode is typically stored in a read only memory (ROM), or a programmable logic array (PLA) structure forming a part of the microprocessor integrated circuit.
Since the first microprocessor was introduced, microprocessor integrated circuits have markedly increased both in the complexity and number of microinstructions that may be carried out, and in the number of circuit elements that can be incorporated in a single integrated circuit, with improvements in integrated circuit design and fabrication technology.
However, as the capabilities of microprocessors increase, users and potential users of microprocessors continually devise more sophisticated and demanding desired performance characteristics in a microprocessor. For example, embedded computer systems, such as automatic flight controllers, inertial navigation systems or industrial controllers require high precision computation done on rapidly changing "real life" variables. In such systems, the computed results have to be fed back in real time, i.e., within micro or milliseconds, to other parts of the systems to close the appropriate control loop. In particular, the instruction set architecture specified by MIL-STD-1750A (Notice 1) requires considerable improvement in microprocessor design for implementation. MIL-STD-1750A is of particular relevance for flight control systems, but similar demands are made by other real time processing environments, such as in data collection systems for nuclear physics experiments, radar data interpretation systems, rapid transit vehicle control, and even certain "on line" business applications. Such real time processing environments, for example, require high throughput and precision so that the results of data processing are available in time and in an accurate form to influence the process or system being monitored or controlled. In summary, such systems require a high performance microprocessor with both accurate floating point and fixed point arithmetic, and comprehensive interrupt and fault handling.